A cellular communication system can support bi-directional communication for multiple users by sharing the available system resources. Cellular systems are different from broadcast systems that can mainly or only support unidirectional transmission from broadcast stations to users. Cellular systems are widely deployed to provide various communication services and may be multiple-access systems such as Code Division Multiple Access (CDMA) systems, Time Division Multiple Access (TDMA) systems, Frequency Division Multiple Access (FDMA) systems, Orthogonal FDMA (OFDMA) systems, Single-Carrier FDMA (SC-FDMA) systems, etc.
A cellular system may support broadcast, multicast, and unicast services. A broadcast service is a service that may be received by all users, e.g., news broadcast. A multicast service is a service that may be received by a group of users, e.g., a subscription video service. A unicast service is a service intended for a specific user, e.g., voice call. Group communications can be implemented using either unicast, broadcast, multicast or a combination of each. As the group becomes larger it is generally more efficient to use multicast services.
Certain push-to-talk (PTT) solutions offer group priority access, thereby improving the chance of high priority group members to access the network by reducing the access channel collision. This is achieved by preventing other low priority users from performing channel access procedures when a select high priority group call is placed. However, generic 3rd Generation Partnership Project (3GPP) or 3GPP2 networks cannot support such application layer group priority.
Long Term Evolution (LTE) networks support access barring by broadcasting the class(es) or categories of subscribers barred from network access on a cell-by-cell basis, as indicated in a System Information Block (SIB) message. UEs are provisioned with one or more access classes, and if at least one access class on the UE is permitted access based on the SIB message, the UE is allowed to perform access attempts. The typical use of access class-based barring is to categorize users into two ranges: the range that is barred from access and the remaining set that is allowed access.
This access barring is not group specific, however, and affects all of the users in a particular access class of UE calls. Moreover, LTE access barring is not dynamic, i.e., operator intervention is required to change the access barring information in the SIB message. Further, the access barring lasts even after the high priority user has completed access and bearer assignment.